...a company such as Red Hat, or Novell's SuSE Linux but rather from the version that project leader Linus Torvalds posts periodically to kernel.org.
Among the open source technologies used by Google are the Python programming language and the MySQL database, he said. In addition, Google's Blogger site uses Apache web server software and the Tomcat package for running Java programs on the server.
The GCC compiler software, used to create nearly every open source program in existence, also is widely used at Google.
Sun's Java also figures prominently, even though it's not open source. "We make great use of Java at the company," DiBona said, including for Gmail. The company claims the web-based email service has millions of subscribers.
Sun hasn't released the fundamental part of Java — the virtual machine component — as open source software. However, the Apache Software Foundation is working on an open source Java effort called Project Harmony, an initiative that now has IBM developer support.
"I think they'll succeed wildly," DiBona said of Harmony. "They're so good at this. They say, 'We're going to write this software,' and it gets done."
Despite Google's liking for open source software, plenty of programming at the company is proprietary.
"We're never going to open source PageRank," DiBona said, referring to the algorithm the company uses to choose which search results to present. "It's the thing that makes Google Google."
Google isn't only an open source software consumer. It's an open source producer as well. For example, employees submit software to the Apache Axis Web services project, DiBona said.
Google also has published several open source projects, including tools for debugging software, improving its performance, monitoring MySQL databases and using AJAX. But so far, there is a significant limit to the group-programming facet of Google's projects: The company doesn't yet accept outside contributions.
Some developers have offered the company contributions meant to improve Google's open source software — for example, to add 64-bit support to 32-bit software. That cooperation is awkward right now for reasons relating to intellectual-property control, DiBona said.
"We've been slow in being able to accept outside patches," he said. But the company is working on a contributor licence that lays out patent and copyright terms for outside contributors. "It's something that pays to be very, very careful about."
The company has helped outside open-source projects, though. Through a $2m programme called the Google Summer of Code, the company sponsored 400 college-age students to work on open-source projects last summer. Each got $4,500 if they met their goals, which 84 percent did. Another $500 went to each of the several open-source projects that helped organise the effort, DiBona said.
Open source software is good for young programmers, DiBona said, noting that it gives them real-world problems to solve and teaches them self-management skills.
"We think open source is pretty important," DiBona said. "Without it, the industry would not be as good as it is now to newcomers."
